1. Field of the Invention
The present invention relates to an image-forming device, and in particular, to a paper-discharging apparatus discharging an image-printed paper to the outside of -a body of an image-forming device.
2. Description of the Related Art
FIG. 1 illustrates an inside of a conventional image-forming device 100, such as an ink-jet printer by way of an example, among various types of image-forming devices, such as an electrophotographic type printer, a copying machine, an ink-jet printer, etc. Referring to FIG. 1, the conventional image-forming device 100 comprises a paper-feeding apparatus 120 feeding a paper, a paper transfer path 130 defined in the inside of a body 110 of the image-forming device to connect the paper-feeding apparatus 120 and a paper-discharging port (not shown), an ink cartridge 140, and a paper-discharging apparatus 150 discharging a printed paper printed by the ink cartridge 140. Reference numeral 145 denotes a carriage accommodating the ink cartridge, in which a carriage is mounted within the body 110 of the image-forming device in such a way that the carriage is transversely movable in an arrowed direction a of FIG. 1.
FIG. 2 illustrates the paper-discharging apparatus 150 extracted from the above-mentioned image-forming device 100 of FIG. 1. Referring to FIGS. 1 and 2, the conventional paper-discharging apparatus 150 comprises one or more paper-discharging rollers 151, a supporting plate 153, a supporting bracket 155, and one or more idle rollers 157.
The paper-discharging rollers 151 are rotatably installed within the body 110 of the image-forming device 100 to be disposed adjacent to the paper-discharging port formed through a side of the body 110 of the image-forming device 100, and are rotationally driven by receiving power from a rotational driving unit (not shown).
The supporting plate 153 is fixed within the body 110 of the image-forming device 100 to face the discharging rollers 151, while the paper transfer path 130 is located between the supporting plate 153 and the discharging rollers 151.
The supporting bracket 155 is installed on the bottom side of the supporting plate 153 to face the paper discharging rollers 151, and the one or more idle rollers are rotatably mounted on the bottom side of the supporting bracket 155 in such a way that the idle rollers 157 mate with the paper-discharging rollers 151, respectively.
The supporting bracket 155 and the supporting plate 153 are firmly connected with each other without any gap formed therebetween by a number of clamping bosses 155a and clamping elements 159.
Meanwhile, the idle rollers 157 are arranged so that circumferential surfaces of the idler rollers 157 come into contact with circumferential surfaces of the paper-discharging rollers 151, respectively. As a result, each idle roller 157 rotates in cooperation with the rotationally driven paper-discharging rollers 151, and when the paper-discharging rollers 151 are rotationally driven, a printing paper is transferred toward the paper-discharging port while passing between the idle rollers 157 and the paper-discharging rollers 151.
Because the idle rollers 157 are rotatably supported on the supporting bracket 155 by one or more rotary shafts 158 each formed of a coil spring, the idle rollers 157 are vertically and elastically movable by an external force within limits of elasticity of the rotary shafts 158. Thereby, the idle rollers 157 and/or the paper-discharging rollers 151 can elastically move to compensate for a change of a contact pressure applied to contact surfaces of the idle rollers 157 and the paper-discharging rollers 151. The change of the contact pressure may be caused when a transfer of the printing paper is abnormally executed or when some components of the paper-discharging apparatus 150 are subjected to shape deformation.
The elastic moving limits of the idle rollers 157 and/or the paper-discharging rollers 151 are restricted within a predetermined range in such a way that the contact pressure between each pair of rollers 151 and 157 required to transfer the printing paper can be maintained over a predetermined level. Due to this, when the shape deformation of the supporting plate 153 or the supporting bracket 155 is beyond the elastic movable limits, the loads produced in response to the shape deformation are exerted on only some of the idle rollers 157. In particular, as shown in FIG. 3, if the shape deformation of the supporting plate 153 exceeds the elastically movable limits, the shape deformation of the supporting plate 153 causes the shape deformation of the supporting bracket 155, thereby resulting in that the idle rollers 157 are disposed to be spaced-apart from the paper-discharging rollers 151 beyond a proper gap required to maintain the contact pressure at a predetermined level or to be excessively compressed with respect to the paper-discharging rollers 151. Due to this shape deformation, a so-called skew phenomenon, in which the printing paper is discharged in a direction having an angle with the paper transfer path 130, is generated, and an image is obliquely printed on the printing paper. In addition, there will be caused a problem that a part of the image printed on the printing paper may be damaged by the idle rollers 157 excessively pressing against the paper-discharging rollers 151 as described above.